CN106411802A - Frequency offset correction method based on unmanned aerial vehicle data link transmission - Google Patents
Frequency offset correction method based on unmanned aerial vehicle data link transmission Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
Abstract
The invention discloses a frequency offset correction method based on unmanned aerial vehicle data link transmission and belongs to the field of unmanned aerial vehicle data link signal processing. The method is based on a system and the system comprises signal generation, modulation, channel noise adding, decision-feedback phase-locked loop and sampling modules; the method comprises the following steps that S1.an arc tangent phase discriminator carries out arc tangent on I path and Q path of signals of modulated signals to obtain modulated signal phase information; S2.the arc tangent phase discriminator compares the previous output of a digital-controlled oscillator with a modulated signal phase, computes a phase difference between the two and adjusts the phase difference to a correct constellation point angle range; S3.a digital filter loop carries out loop filtering on the phase difference output in S2 in order to obtain step quantity; S4.the digital-controlled oscillator adjusts the previous estimated value output by the digital-controlled oscillator with the step quantity as a unit in order to obtain a new estimated value; and S5.the S2 to S4 are repeated for N times to obtain a more accurate estimated value, so that coherent carriers are generated, and the correction of the frequency offset is realized, wherein N is a simulation number of symbols and the value range is from 5000 to 1000000.
Description
Technical field
The present invention relates to a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission, belong to frequency offset correction and unmanned
Machine Data-Link field of signal processing.
Background technology
During Unmanned Aerial Vehicle Data Link transmission, total two paths of signals is operated, and wherein one road is used as remote measuring and controlling,
Another road is used as image transmitting, and in order to ensure picture quality, on the premise of total transmission power is certain, image transmitting branch road needs
Obtain relatively high power, and remote measuring and controlling branch road distribution less power, Given this using uneven quaternary PSK (UQPSK) this
Plant modulation system.Receiver needs to realize coherent demodulation with coherent carrier, because the frequency that the factors such as Doppler frequency shift lead to is inclined
Move and recovery coherent carrier is had a significant impact.
In the technology that existing correcting frequency shift realizes carrier synchronization, pilot tone system is led because in addition transmitting terminal need to send
Frequency signal, reduces band efficiency and power utilization；Estimate coherent carrier thus correcting the skill of frequency deviation from modulated signal
In art, quadratic loop and biquadratic ring etc., due to can introduce nonlinear component using square law device, are difficult to work in high frequency simultaneously
Section and the occasion of two-forty；COSTAS ring structure is simple, but realizes complex under high-order modulating, is difficult to work simultaneously
Make in the occasion of two-forty.
(1) exist《Railway communication and signaling engineering technology (RSCE)》In August, 2014 the 4th phase of volume 11, entitled：" low noise
The principle of carrier synchronization in carrier synchronization method than lower inductive communication spread-spectrum signal " article, is solved the problems, such as according to phaselocked loop, if
Count the vicariouss spread spectrum communication system based on decision-feedback phaselocked loop, solve carrier synchronization in the case of low signal-to-noise ratio
The undesirable difficult problem of performance.However, the cyclic process of the method comprises despreading, demodulation, sampling and judgement and decision-feedback lock
Phase ring generates carrier wave, computationally intensive, takies resource many；Extract phase place letter with autocorrelative method in decision-feedback phaselocked loop
Breath, but the method is not suitable for this modulation system of UQPSK；Though comprising decision-feedback phaselocked loop in article in addition, fail straight
Connect and reduce later stage operand using the function that it is adjudicated.
(2) application number：201510797097.8, entitled " the spread-spectrum signal Frequency offset estimation side based on decision-feedback
Method ", process include frequency deviation precorrection, correction result related to leading symbol spread-spectrum code chip, de-spread, store despread symbols, difference
Process, frequency deviation is carefully estimated and accurate offset estimation value, effectively increases offset estimation performance.Although this application has offset estimation
The high feature of accuracy, but it is loaded down with trivial details to there is process, computationally intensive, the defect such as molding structure complexity.
Although above-mentioned existing frequency offset correction techniques calibration accuracy is high, resource utilization is low and operand
Greatly, also there is significant improvement space, for being simultaneous for the actual demand of Unmanned Aerial Vehicle Data Link transmission, have significant limitations.This
Invention is devoted to solving above-mentioned technological deficiency it is proposed that a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission.
Content of the invention
, according in Unmanned Aerial Vehicle Data Link Transmission system, image transmitting branch road is with remote measuring and controlling branch road distribution power not for the present invention
With demand, using the modulation system of UQPSK, be devoted to simultaneously for operand in prior art big, resources occupation rate is high, no
Method is applied to two-forty, altofrequency and uses the defect of the occasion of high-order modulating it is proposed that a kind of be based on Unmanned Aerial Vehicle Data
The frequency deviation correcting method of chain transmission.
A kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission, abbreviation this method；
For solving above-mentioned technical problem, this method adopts the following technical scheme that：
The system that this method is relied on includes signal generating module, modulation module, channel adds module of making an uproar, decision-feedback locks phase
Ring module and sampling module；
Signal generator is comprised in described signal generating module；Described modulation module comprises multiplier；
Described channel adds module of making an uproar and specifically includes generation additive white Gaussian noise and add this to be additive white Gaussian noise
In system；
Described decision-feedback phase-locked loop module includes arc tangent phase discriminator, digital loop filters and digital controlled oscillator；
Preferably, decision-feedback phaselocked loop is second-order loop phaselocked loop；
Preferably, digital loop filters are the digital model of active proportional-integral filter；This method is relied on
The each functions of modules of system is as follows：
The function of described signal generating module is to generate baseband signal and carrier wave；
The function of described modulation module is by baseband signal and carrier multiplication, realizes modulation；
The function that described channel adds module of making an uproar is the extraneous impact to system for the noise signal in simulating reality operation；
The function of described decision-feedback phase-locked loop module is to realize the correction of frequency shift (FS)；
Wherein, in decision-feedback phaselocked loop, the function of each module is as follows：
The function of arc tangent phase discriminator is to estimate that phase information obtains for comparing modulated signal phase information and phaselocked loop
Phase information, and by the angular range of adjusting offset to the correct constellation point of system, result is input to digital loop filtering
Device；
The function of digital loop filters is that high fdrequency components and noise are risen with the school of inhibitory action, dynamic control phase-locked loop
Positive accuracy and speed, phase information is carried out with loop filtering and the stepping-in amount obtaining is inputted digital controlled oscillator；
The function of digital controlled oscillator is the phase estimation value of output coherent carrier, and this value every time all can be in units of stepping-in amount
Adjustment, thus obtaining more accurately phase estimation value, to realize the compensation to frequency shift (FS)；
The function of described sampling module is the signal after compensating to be carried out extracting effective information, to recover primary signal；
Decision-feedback phaselocked loop determines its locking time and capture frequency scope, digital rings by the parameter of digital filter
The parameter of path filter is designated as C1 and C2, and this two parameters pass through the closed loop transfer function of decision-feedback phaselocked loop, by formula
(1) it is calculated：
Wherein, H (z) is the closed loop transfer function of decision-feedback phaselocked loop；K0For digital controlled oscillator gain, K1For arc tangent
Phase detector gain；
Shown in the z-transform form such as formula (2) of the closed loop transfer function of standard：
Wherein, TsFor sampling time interval, ζ is damped coefficient, and its span is 0.6 to 1；Preferably ζ takes 0.707；
ωnFor natural angular frequency, by equivalent noise bandwidth BLObtain；
Formula (1) can be obtained with formula (2) contrast：
This method, comprises the steps：
S1, arc tangent phase discriminator receive modulated signal, then the I road signal of modulated signal and Q road signal are carried out arc tangent,
Obtain the phase information of modulated signal；
Wherein, modulated signal includes I roadbed band signal and Q roadbed band signal；I roadbed band signal abbreviation I road signal, is designated as
I；Q roadbed band signal abbreviation Q road signal, is designated as Q；
The phase information of the modulated signal receiving is designated as θs, calculated by equation below (4)：
θs=arctan (I/Q) (4)；
S2, the carrier phase estimated value of more previous digital controlled oscillator output of arc tangent phase discriminator and modulated signal phase place
Information calculates phase contrast between the two, then by this adjusting offset to correct constellation point angular range；
Wherein, carrier phase estimated value, is designated as θout_0；Modulated signal phase information, is designated as θs, this phase place between the two
Difference, is designated as Δ θ, is calculated by equation below (5)：
Δ θ=θs-θout_0(5)；
Phase contrast after adjustment is designated as Δ θ ', as the output of arc tangent phase discriminator；
S3, digital loop filters carry out loop filtering to the phase contrast that S2 exports, and are digitally controlled the stepping-in amount of agitator；
Wherein, the stepping-in amount of digital controlled oscillator, is designated as NCO_Step, is calculated by equation below (6)：
NCO_Step=f1(Δθ',C1,C2) (6)；
The carrier phase estimated value that S4, digital controlled oscillator export to previous digital controlled oscillator is with digital controlled oscillator stepping-in amount
It is adjusted for unit, obtain new phase estimation value；
Wherein, the carrier phase estimated value of previous digital controlled oscillator output, is designated as θout_0；Digital controlled oscillator stepping-in amount,
It is designated as NCO_Step；New phase estimation value, is designated as θout_1,
Calculated by equation below (7)：
θout_1=f2(θout_0,NCO_Step) (7)；
S5, repetition S2 to S4N time, obtain the most accurate estimated value, produce coherent carrier with this, realize to frequency shift (FS)
Correction；
Wherein, N represents emulation code element number it is contemplated that accuracy of simulation and memory problem, and the span of N is generally 5000
To 1000000；
So far, from S1 to S5, complete a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission.
Beneficial effect
A kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission, compared with other frequency deviation correcting methods, have as
Lower beneficial effect：
1. institute of the present invention extracting method with《Railway communication and signaling engineering technology (RSCE)》In August, 2014 the 4th phase of volume 11
That delivers is entitled：The method phase used in the article of " carrier synchronization method of inductive communication spread-spectrum signal under low signal-to-noise ratio "
Ratio can not only keep functional in the case of low signal-to-noise ratio, also reduce resources occupation rate, the size of amount of calculation simultaneously
It is improved, and passes through the adjustment to phase contrast in arc tangent phase discriminator, solve due to I road under UQPSK modulation system
The modulation intelligence that signal, Q road signal power are different and lead to cannot eliminate thus cannot get the problem of complete phase information, this
Outward, flexibly use the function of decision-feedback phaselocked loop, omit the judging process after demodulation；
2. institute of the present invention extracting method and Application No. 201510797097.8, entitled " the spread spectrum letter based on decision-feedback
The method used in the patent of number frequency offset estimation methods " is compared, though the order of accuarcy of its estimated value can not be reached, greatly
Simplify greatly calculating process, make the system that this method is relied on be more easy to realize；
3. compared with pilot tone system, need not other pilot signal transmitted, transmission power is applied all to useful signal, simultaneously
Improve band efficiency；
4., compared with around-France with square around-France and biquadratic, method proposed by the invention does not use square law device, thus
Greatly reduce the introducing of nonlinear component and noise, can apply to the occasion of altofrequency, two-forty simultaneously；
5., compared with around-France with COSTAS, though the simple degree of its structure can not be reached, it is not limited to modulation system
Select, the occasion using high-order modulating can be applied to.
Brief description
For the clearer explanation embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing
Have technology description in required use accompanying drawing be briefly described it is clear that, drawings in the following description are the present invention
Some embodiments, for those of ordinary skill in the art, on the premise of not paying creative work, can also basis
These accompanying drawings obtain other accompanying drawings；
Fig. 1 is the frequency deviation school in a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission of the present invention and embodiment 1
Positive system block diagram；
Fig. 2 is the digital rings in a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission of the present invention and embodiment 1
Path filter theory diagram；
Fig. 3 is the arc tangent in a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission of the present invention and embodiment 2
Phase discriminator extracts phase contrast the schematic flow sheet correcting；
Fig. 4 is a kind of warp being applied to based on the frequency deviation correcting method of Unmanned Aerial Vehicle Data Link transmission in embodiment 3 of the present invention
Cross the signal constellation (in digital modulation) figure measured result after decision-feedback phaselocked loop compensates；
Fig. 5 be the present invention a kind of be applied to based on the frequency deviation correcting method of Unmanned Aerial Vehicle Data Link transmission in embodiment 3 be
System ber curve measured result.
Specific embodiment
Purpose, technical scheme and advantage for making the embodiment of the present invention are clearer, below in conjunction with the embodiment of the present invention
In accompanying drawing, the technical scheme in the embodiment of the present invention is carried out with clear, complete description it is clear that described embodiment is
The a part of embodiment of the present invention, rather than whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art
Obtained every other embodiment on the premise of not making creative work, broadly fallen into the scope of protection of the invention.
The present invention is in order to solve the problems, such as existing frequency offset correction method it is proposed that a kind of be based on Unmanned Aerial Vehicle Data Link
The frequency deviation correcting method of transmission, it is achieved that the recovery for coherent carrier in Unmanned Aerial Vehicle Data Link Transmission system, corrects frequency
Rate offsets, and can effectively reduce amount of calculation and resources occupation rate, preferably be applied in altofrequency and the communication system of two-forty,
Meet the demand of high-order modulating, improve band efficiency and power utilization simultaneously.
Embodiment 1
This example illustrates the frequency offset correction system composition of the method for the invention and annexation.
Fig. 1 is the frequency offset correction system block diagram that this method and the present embodiment provide.Understand, this method is relied on referring to Fig. 1
System include signal generating module, modulation module, channel add module of making an uproar, decision-feedback phase-locked loop module and sampling module；Institute
State signal generating module and adopt signal generator, produce baseband signal and carrier wave as the input of modulation module；Described modulation mould
Block adopts multiplier, baseband signal and carrier multiplication is realized modulation, the signal after modulation is as the input of channel plus module of making an uproar；
Described channel adds module of making an uproar and adopts additive white Gaussian noise, and the signal after modulation is added simulation reality with additive white Gaussian noise should
With during noise jamming；Described decision-feedback phase-locked loop module includes arc tangent phase discriminator, digital loop filters sum
Controlled oscillator, the phase information obtaining is used for producing coherent carrier, then realizes demodulation with the signal multiplication adding after making an uproar, as sampling
The input of module；Sampling module, by the sampling to signal after demodulating, recovers original baseband signal.
In Fig. 1, decision-feedback phaselocked loop determines its locking time and capture frequency scope by the parameter of digital filter,
The principle schematic being embodied as is as shown in Figure 2.
Arc tangent phase discriminator from figure 2 it can be seen that the input of digital loop filters is X (k), after as adjusting
Phase information；Output is G (k), and as phase information is carried out with the result of loop filtering；C1 is multiplied by C1 branch road with X (k)
As the result of C1 branch road, the chronotron of C2 branch road passes through the delay of a unit, obtains the delayed data of X (k), then by time delay
The result that the result that information is added with X (k) is multiplied as C2 branch road with C2, G (k) is C1, C2 two branch road result sum；Wherein
The parameter C1 and C2 closed loop transfer function by decision-feedback phaselocked loop, is specifically calculated by formula (1)；
In formula (1), H (z) is the closed loop transfer function of decision-feedback phaselocked loop；K0For digital controlled oscillator gain, K1For anti-
Tangent phase detector gain；
In theory shown in the z-transform form such as formula (2) of the closed loop transfer function of standard；
In formula (2), TsFor sampling time interval, ζ is damped coefficient, and its span is 0.6 to 1；Preferably ζ takes
0.707；ωnFor natural angular frequency, by equivalent noise bandwidth BLObtain；
Formula (1) can be obtained formula (3), the as expression formula of parameter C1 and C2 with formula (2) contrast.
Embodiment 2
The present embodiment is specifically described arc tangent phase discriminator in the method for the invention and extracts phase contrast the flow process correcting.
Fig. 3 is the method for the invention and the present embodiment arc tangent phase discriminator extraction phase contrast providing the flow process correcting
Schematic diagram.
From the figure 3, it may be seen that the flow process that arc tangent phase discriminator extracts phase contrast and corrects is as follows：
First, input signal arc tangent, represent that arc tangent phase discriminator does arc tangent to the modulated signal of input；
Second, it is to seek phase contrast, that is, arc tangent phase discriminator extracts the phase information of modulated signal, secondly will be previous
Carrier phase estimated value is compared with the phase information of modulated signal and obtains phase contrast；
3rd, do mould 2 π process, will phase contrast be mould 2 π process move to 0～2 π so that making the difference result；
4th, limit phase place, that is, try to achieve correct constellation point in-scope, facet phases as limit phase place；
5th, phase place, the phase signal after being adjusted in the phase-rotated phase range to restriction；
So far, through the result of the above-mentioned first to the 5th step, the as output of arc tangent phase discriminator.
Embodiment 3
The present embodiment is specifically described Unmanned Aerial Vehicle Data Link transmission system under UQPSK modulation system for the method for the invention
Implementation process in system.
Below taking the Unmanned Aerial Vehicle Data Link Transmission system under UQPSK modulation system as a example, being embodied as to the present invention
Journey illustrates.The system clock of described Unmanned Aerial Vehicle Data Link Transmission system is 2MHz, and modulation system is UQPSK, wherein observing and controlling
Branch road I road is 1 with the power ratio on image transmitting branch road Q road:4, the spreading ratio of observing and controlling branch road is 512, specifically includes following step
Suddenly：
Step a, setting loop filter parameters C1, C2；
Step b, arc tangent phase discriminator do arc tangent to the I road signal of modulated signal and Q road signal, obtain modulated signal
Phase information is as normalized phase；
The phase estimation value of previous to digital controlled oscillator output of step c, arc tangent phase discriminator and normalized phase make the difference, and obtain
To phase signal；
Step d, arc tangent phase discriminator will carry out mould 2 π process in the phase contrast of interval [- 3 π, π], and the phase contrast obtaining exists
Change between [0,2 π] scope；
The ratio of step e, I road signal and Q road signal power is 1:4, that is, the ratio of the amplitude on planisphere is 1:2, system is just
It is 1 that UQPSK planisphere after really catching should be wide and long ratio:2 rectangle, therefore facet phases are restriction phase place, that is,
For arctan (1/2)；
Step f, in arc tangent phase discriminator, the phase contrast that each quadrant exceedes restriction all takes boundary value, only retains effectively
Phase contrast in region, and rotated interval interior to [- arctan (1/2), arctan (1/2)]；
Step g, digital loop filters carry out loop filtering, suppression high fdrequency components and noise to phase contrast, simultaneously with number
Word loop filter parameters act on, and obtain controlling the stepping-in amount of digital controlled oscillator；
If step h stepping-in amount>0, then digital controlled oscillator increase on the basis of previous phase estimation value；If stepping
Amount<0, then digital controlled oscillator reduce on the basis of previous phase estimation value；
Step I, system adopt final phase estimation value, produce coherent carrier accordingly, realize the correction of frequency shift (FS).
Understand from the description above, by repeatedly and normalized phase comparison so that final estimated value is ideal
Phase value.Can solve the problem that following defect using this kind of decision-feedback phaselocked loop：
(A) with《Railway communication and signaling engineering technology (RSCE)》It is entitled that in August, 2014 the 4th phase of volume 11 delivers：
The method used in the article of " carrier synchronization method of inductive communication spread-spectrum signal under low signal-to-noise ratio " is compared, and this method is in step
In b, the phase information of modulated signal is extracted, the cyclic process of step c to step h is all that phase signal is operated, loop ends
Obtain producing again coherent carrier during optimum phase estimated value, operand is less；And the cyclic process of method therefor comprises in article
Despreading, demodulation, sampling and judgement and decision-feedback phaselocked loop generate carrier wave, computationally intensive, take resource many；
This method passes through the adjustment to phase contrast in arc tangent phase discriminator to step f of step d, solves due to UQPSK
The modulation intelligence that I road signal under modulation system, Q road signal power are different and lead to cannot eliminate thus cannot complete phase letter
The problem of breath；And in article method therefor when running into the different signal of I road signal, Q road signal power, the result of related operation
Modulation intelligence cannot be eliminated, therefore cannot extract phase place；
This method applies flexibly the function of decision-feedback phaselocked loop, need not adjudicate after the sampling, and in article method therefor is still
Need to adjudicate, increased operand；
(B) with Application No. 201510797097.8, entitled " the spread-spectrum signal Frequency offset estimation based on decision-feedback
The method used in the patent of method " is compared, and this method is constantly estimated to the phase place of previous digital controlled oscillator generation by step h
Evaluation is adjusted in units of stepping-in amount, obtains ideal phase value, though estimated result can not reach very high standard
Really degree, but enormously simplify calculating process, it is easy to accomplish；And the estimation procedure of method therefor includes the pre- school of frequency deviation in patent
Just, correction result is related to leading symbol spread-spectrum code chip, de-spread, store despread symbols, difference processing, frequency deviation are carefully estimated and accurately
Offset estimation value, though accuracy is high, process is loaded down with trivial details, computationally intensive, and molding structure is complicated；
(C) compared with pilot tone system, this method only need to generate baseband signal and carrier wave in signal generating module, need not in addition send out
Send pilot signal, transmission power is applied all to useful signal, improve band efficiency simultaneously；
(D), compared with around-France with square around-France and biquadratic, step a of this method makes to step h when carrying out frequency offset correction
It is decision-feedback phaselocked loop, can apply to the occasion of altofrequency, two-forty；And quadratic loop and the use square of biquadratic ring
Rate device, is easily caused the introducing of nonlinear component and noise, when the carrier frequency is high, square or biquadratic after frequency difficult
To realize it is impossible to meet the requirement of altofrequency, two-forty；
(E) compared with around-France with COSTAS, though this method can not reach the simple degree of its structure, it is not limited to modulate
Way choice, can be applied to the occasion using high-order modulating, and such as UQPSK, 8PSK etc. can be in steps e
Different branch signal is processed；And COSTAS ring structure is simple, it is basically used for BPSK, QPSK being used as the field of modulation system
Close.
To verify the effect of above-described embodiment methods described below by experiment.
The system clock of Unmanned Aerial Vehicle Data Link Transmission system described in this experiment is 2MHz, and modulation system is UQPSK, wherein
Observing and controlling branch road I road is 1 with the power ratio on image transmitting branch road Q road:4, the spreading ratio of observing and controlling branch road is 512.
Fig. 4 is the signal constellation (in digital modulation) figure measured result after decision-feedback phaselocked loop compensates.
The signal that in Fig. 4, planisphere is reacted, be with using after frequency offset correction coherent carrier demodulation after signal, Fig. 4
Middle abscissa represents phase place, vertical coordinate represent phase shift it is clear that, decision-feedback phaselocked loop acquisition success and frequency offset correction
Accurately；
On the other hand, an assessment is done to the reliability of system, make signal to noise ratio in the range of -5dB to 12dB, the bit error rate is bent
Line is as shown in Figure 5.
In Fig. 5, abscissa is signal to noise ratio (EbNo), and vertical coordinate is the bit error rate (Pe_UQPSK).From fig. 5, it can be seen that when letter
Make an uproar ratio during more than -3dB, the ber curve of emulation is close to ideal ber curve, functional, highly reliable.
In sum, the application method of the present invention can realize the correction of the frequency shift (FS) to Unmanned Aerial Vehicle Data Link transmission,
Complete carrier synchronization, with respect to the method for the carrier synchronization of existing correcting frequency shift, decrease operand, improve frequency band
And power utilization, applicable situation is more extensive.
Above example is merely to illustrate technical scheme, is not intended to limit；Although with reference to the foregoing embodiments
The present invention has been described in detail, it will be understood by those within the art that：It still can be to aforementioned each enforcement
Technical scheme described in example is modified, or carries out equivalent to wherein some technical characteristics；And these are changed or replace
Change, do not make the essence of appropriate technical solution depart from the spirit and scope of various embodiments of the present invention technical scheme.
Claims (7)
1. a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission, abbreviation this method it is characterised in that：Relied on is
System includes signal generating module, modulation module, channel add module of making an uproar, decision-feedback phase-locked loop module and sampling module；
Signal generator is comprised in described signal generating module；Described modulation module comprises multiplier；
Described channel adds module of making an uproar and specifically includes generation additive white Gaussian noise and add additive white Gaussian noise in the system；
Described decision-feedback phase-locked loop module includes arc tangent phase discriminator, digital loop filters and digital controlled oscillator.
2. a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission as claimed in claim 1, is further characterized in that：This
The each functions of modules of system that method is relied on is as follows：
The function of described signal generating module is to generate baseband signal and carrier wave；
The function of described modulation module is by baseband signal and carrier multiplication, realizes modulation；
The function that described channel adds module of making an uproar is the extraneous impact to system for the noise signal in simulating reality operation；
The function of described decision-feedback phase-locked loop module is to realize the correction of frequency shift (FS)；
Wherein, in decision-feedback phaselocked loop, the function of each module is as follows：
The function of arc tangent phase discriminator is to estimate that phase information obtains phase place for comparing modulated signal phase information and phaselocked loop
Difference information, and by the angular range of adjusting offset to the correct constellation point of system, result is input to digital loop filters；
The function of digital loop filters is that high fdrequency components and noise are risen with the correction essence of inhibitory action, dynamic control phase-locked loop
Degree and speed, phase information is carried out loop filtering and by the stepping-in amount obtaining input digital controlled oscillator；
The function of digital controlled oscillator is the phase estimation value of output coherent carrier, and this value all can be adjusted every time in units of stepping-in amount
Whole, thus obtaining more accurately phase estimation value, to realize the compensation to frequency shift (FS)；
The function of described sampling module is the signal after compensating to be carried out extracting effective information, to recover primary signal；
Decision-feedback phaselocked loop determines its locking time and capture frequency scope by the parameter of digital filter, and digital loop is filtered
The parameter of ripple device is designated as C1 and C2, and this two parameters pass through the closed loop transfer function of decision-feedback phaselocked loop, is counted by formula (1)
Obtain：
Wherein, H (z) is the closed loop transfer function of decision-feedback phaselocked loop；K0For digital controlled oscillator gain, K1For arc tangent phase demodulation
Device gain；
Shown in the z-transform form such as formula (2) of the closed loop transfer function of standard：
Wherein, TsFor sampling time interval, ζ is damped coefficient, and its span is 0.6 to 1；Preferably ζ takes 0.707；ωnFor
Natural angular frequency, by equivalent noise bandwidth BLObtain；
Formula (1) can be obtained with formula (2) contrast：
3. a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission as claimed in claim 1, is further characterized in that：Bag
Include following steps：
S1, arc tangent phase discriminator receive modulated signal, then the I road signal of modulated signal and Q road signal are carried out arc tangent, obtain
The phase information of modulated signal；
S2, the carrier phase estimated value of more previous digital controlled oscillator output of arc tangent phase discriminator and modulated signal phase information
Calculate phase contrast between the two, then by this adjusting offset to correct constellation point angular range；
S3, digital loop filters carry out loop filtering to the phase contrast that S2 exports, and are digitally controlled the stepping-in amount of agitator；
The carrier phase estimated value that S4, digital controlled oscillator export to previous digital controlled oscillator is with digital controlled oscillator stepping-in amount as list
Position is adjusted, and obtains new phase estimation value；
S5, repetition S2 to S4N time, obtain the most accurate estimated value, produce coherent carrier with this, realize the school to frequency shift (FS)
Just；
Wherein, N represents emulation code element number it is contemplated that accuracy of simulation and memory problem, and the span of N generally arrives 5000
1000000；
So far, from S1 to S5, complete a kind of frequency deviation correcting method for Unmanned Aerial Vehicle Data Link transmission.
4. a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission as claimed in claim 3, is further characterized in that：
In S1, modulated signal includes I roadbed band signal and Q roadbed band signal；I roadbed band signal abbreviation I road signal, is designated as I；Q
Roadbed band signal abbreviation Q road signal, is designated as Q；
The phase information of the modulated signal receiving is designated as θs, calculated by equation below (4)：
θs=arctan (I/Q) (4).
5. a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission as claimed in claim 3, is further characterized in that：S2
In, carrier phase estimated value, it is designated as θout_0；Modulated signal phase information, is designated as θs, this phase contrast between the two, it is designated as Δ θ,
Calculated by equation below (5)：
Δ θ=θs-θout_0(5)
Phase contrast after adjustment is designated as Δ θ ', as the output of arc tangent phase discriminator.
6. a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission as claimed in claim 3, is further characterized in that：S3
In, the stepping-in amount of digital controlled oscillator, it is designated as NCO_Step, calculated by equation below (6)：
NCO_Step=f1(Δθ',C1,C2) (6).
7. a kind of frequency deviation correcting method based on Unmanned Aerial Vehicle Data Link transmission as claimed in claim 3, is further characterized in that：S4
In, the carrier phase estimated value of previous digital controlled oscillator output, it is designated as θout_0；Digital controlled oscillator stepping-in amount, is designated as NCO_
Step；New phase estimation value, is designated as θout_1,
Calculated by equation below (7)：
θout_1=f2(θout_0,NCO_Step) (7).
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